OBJECTIVEAdult glioblastoma (GBM) has proven refractory to decades of innovation. Oncolytic viral therapy represents a novel therapy that uses viral vectors as both a delivery and therapeutic mechanism to target GBM cells. Despite the growing body of basic science data supporting the feasibility of viral therapy to treat GBM, the reporting of clinical trial results is heterogeneous. Correspondingly, the aim of this study was to present a contemporary summary of the progress all clinical trials have made to date.METHODSThe ClinicalTrials.gov database was reviewed in August 2020 for all possible interventional clinical trials involving viral vector–based therapy to treat adult GBM. These were then screened against selection criteria to identify pertinent clinical trials.RESULTSA total of 29 oncolytic viral therapy trials treating adult GBM were identified. The median start and expected completion years were 2014 and 2020, respectively. At the time of this writing, 10 (35%) trials were reported to have completed recruitment, whereas 7 (24%) were actively recruiting. The median target enrollment number was 36 (range 13–108), with the majority of trials being phase I (n = 18, 62%), and involving secondary GBM among other malignant glioma (n = 19, 66%). A total of 10 unique viral vectors were used across all trials, with the most common being adenovirus (n = 16, 55%). Only 2 (7%) phase I trials to date have reported outcomes on the ClinicalTrials.gov portal. Results of 12 additional clinical trials were found in academic publications, with median progression-free and overall survival times of 3 and 15 months, respectively, after the first viral dose at recurrence. The coordination of the large majority of trials originated from the US (n = 21, 72%), and the median number of testing sites per trial was 1 (range 1–15), via industry funding (n = 18 trials, 62%).CONCLUSIONSThere are multiple early-stage oncolytic viral therapy clinical trials for adult GBM currently active. To date, limited results and outcomes are promising but scarce. The authors expect this to change in the near future because many trials are scheduled to have either nearly or actually reached their expected recruitment completion time. How exactly oncolytic viral therapy will fit into the current treatment paradigms for primary and secondary GBM remains to be seen, and will not be known until safety and toxicity profiles are established by these clinical trials.

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Glioblastoma (GBM) remains one of the most lethal primary brain tumors in both adult and pediatric patients. Targeting tumor metabolism has emerged as a promising-targeted therapeutic strategy for GBM and characteristically resistant GBM stem-like cells (GSCs). Neoplastic cells, especially those with high proliferative potential such as GSCs, have been shown to upregulate UCP2 as a cytoprotective mechanism in response to chronic increased reactive oxygen species (ROS) exposure. This upregulation plays a central role in the induction of the highly glycolytic phenotype associated with many tumors. In addition to shifting metabolism away from oxidative phosphorylation, UCP2 has also been implicated in increased mitochondrial Ca2+ sequestration, apoptotic evasion, dampened immune response, and chemotherapeutic resistance. A query of the CGGA RNA-seq and the TCGA GBMLGG database demonstrated that UCP2 expression increases with increased WHO tumor-grade and is associated with much poorer prognosis across a cohort of brain tumors. UCP2 expression could potentially serve as a biomarker to stratify patients for adjunctive anti-tumor metabolic therapies, such as glycolytic inhibition alongside current standard of care, particularly in adult and pediatric gliomas. Additionally, because UCP2 correlates with tumor grade, monitoring serum protein levels in the future may allow clinicians a relatively minimally invasive marker to correlate with disease progression. Further investigation of UCP2’s role in metabolic reprogramming is warranted to fully appreciate its clinical translatability and utility.